In order to obtain a relatively comprehensive picture of the functional capacity of the heart it is absolutely necessary to perform examinations under dynamic stress. The evaluation of an ECG during and immediately following ergometric stress presupposes a knowledge of the normal ECG pattern and also the characteristic pathological reactions. The ST changes and rhythm disturbances demand special attention. This article covers the most common normal and pathological patterns in addition to discussing several particular aspects of electrocardiograms taken during and after stress as well as their clinical importance.